Co-ownership occurs whenever the ownership of an undivided thing or right belongs to different persons. The share of the co-owners, in the benefits as well as the charges, shall be proportional to their respective interests and any stipulation in a contract to the contrary shall be void. The presumption is, unless the contrary is proved, the portions of the co-owners in a co-ownership shall be equal.
Nonetheless, no co-owner shall be obliged to remain in the co-ownership such that, each one may demand the partition of the thing owned in common at any time. However, when there is an agreement to keep the property undivided for a certain period of time, such shall not exceed ten years at any given term and may be extended by a new agreement.
As for a property which is subject of a donation or a testamentary bequest, the donor or testator may prohibit partition for a period which shall not exceed twenty years.
Partition may be made in two modes: by agreement of the parties which is voluntary partition, and by judicial proceedings. Voluntary partition shall be governed by the provisions stated in the agreement of the parties unless such is expressly prohibited by law. Partition by judicial action shall be governed by the Rules of Court.
(Book II, Title III, Articles 484-501 of the Civil Code of the Philippines)